scope:

INTRODUCTION

Nitrification is a microbiological process by which reduced nitrogen compounds (primarily ammonia) are sequentially oxidized to nitrite and nitrate (AWWA and EES 2002). Nitrification can be problematic in potable water systems that use chloramines for residual (or secondary) disinfection. The objectives of this manual are to:

• summarize existing knowledge and provide updated information on the current practices of water suppliers and issues related to nitrification;

• provide water utilities with the latest information on nitrification in water distribution systems;

• provide information to help utilities maintain a chloramine residual and overall water quality in tap water; and

• help utilities effectively prevent and mitigate nitrification episodes that may occur in their systems.

There are many sources that discuss the various aspects of nitrification. Several Water Research Foundation (WaterRF) reports discuss nitrification in conjunction with other topics, primarily drinking water disinfection and chloramination. Since the first writing of this manual, a better understanding of chloramination treatment, chloramine residual maintenance, and nitrification control within distribution systems has evolved. This understanding is a result of field experience, research, and pilot studies. For example, water utility personnel understand more fully how to form and monitor chloramine at carefully measured chlorine to ammonia ratios (usually 4.5 or 5.1 Cl2:NH3 -N) with minimal excess ammonia.